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Synlett 2009(10): 1558-1561  
DOI: 10.1055/s-0029-1217336
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Thieme Chemistry Journal Awardees - Where Are They Now? Aerobic Oxidative Coupling of Tertiary Amines with Silyl Enolates and Ketene Acetals

Devarajulu Sureshkumar, Abhishek Sud, Martin Klussmann*
Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
Fax: +49(208)3062980; e-Mail: klusi@mpi-muelheim.mpg.de;
Further Information

Publication History

Received 16 March 2009
Publication Date:
02 June 2009 (online)

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Abstract

Cyclic tertiary amines can be oxidatively coupled with a variety of silyl enol ethers or ketene acetals to furnish tertiary Mannich bases. The reactions are catalyzed by simple copper salts employing elemental oxygen as the oxidant.

Key words

amines - C-H bond functionalization - copper - oxidative cross-coupling - oxidations

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General Procedure for the Oxidative Coupling of Amines
To a solution of the appropriate amine (0.12 mmol, 1.0 equiv) in acetone or MeOH (1.0 mL), the TMS enol ether or silyl ketene acetal (0.30 mmol, 2.5 equiv) and CuCl2˙2H2O (2 mg, 10 mol%) were added, and the mixture was stirred under an atmosphere of oxygen (1 atm) at r.t. After full conversion was achieved, H2O and CH2Cl2 were added and the mixture was extracted with additional CH2Cl2. The combined organic phases were dried over MgSO4 and concentrated in vacuo. The crude residue was purified by flash column chromatography on silica gel (5-10% EtOAc-pentane), giving the product as a solid or oil.